This invention relates generally to electrostatographic printers and copiers or reproduction machines, and more particularly, concerns a dual cam set, segmented transfer assist blade system in which dual sets of cams are rotatable in a first direction and in a second direction for engaging a first set of segmented blades, and a second set of segmented blades, respectively, to contact size image receiving sheets of different widths for assisting in image transfer.
The process of transferring charged toner particles from an image bearing member (e.g. photoreceptor) to an image support substrate (e.g. copy sheet) is enabled by overcoming cohesive forces holding the toner particles to the image bearing member. The interface between the photoreceptor surface and image support substrate is not always optimal. Thus, problems may be caused in the transfer process when spaces or gaps exist between the developed image and the image support substrate. A critical aspect of the transfer process is focused on the application and maintenance of high intensity electrostatic fields in the transfer region for overcoming the cohesive forces acting on the toner particles as they rest on the photoreceptive member. Careful control of these electrostatic fields and other forces is required to induce the physical detachment and transfer-over of the charged toner particles without scattering or smearing of the developer material.
Alternatively, mechanical devices that force the image support substrate into intimate and substantially uniform contact with the image bearing surface have been incorporated into transfer systems. Various contact blade arrangements have been proposed for sweeping the backside of the image support substrate, with a constant force, at the entrance to the transfer region. However, deletions may occur using these methods, especially in duplex copying.
In accordance with the present invention, there is provided a dual cam set transfer assist blade system comprising (a) a first set of cam and blade assemblies mounted on a rotatable shaft and each including a cam having a single lobe for rotation in a first direction to cause engagement of a first set of transfer assist blade segments corresponding to a first set of sheet widths, and (b) a second set of cam and blade also assemblies mounted on the rotatable shaft and each including a cam having a first lobe for rotation in a first direction to cause engagement of a second set of transfer assist blade segments corresponding to said first set of sheet widths, and a second lobe for rotation in a second direction to cause engagement of said second set of transfer assist blade segments corresponding to a second set of sheet widths.